1. Field of the Invention
The present invention relates to cam mechanisms used for forming the shed in weaving machines.
2. History of the Related Art
The term "cam mechanism" is known generally to designate an assembly comprising a series of rocking levers, in a number equal to that of the heddle frames mounted on the weaving machine. Each rocking lever, coupled to one of the frames, is provided with two rollers which cooperate with the two sectioned tracks of a complementary cam driven in rotation by a common shaft connected to that of the corresponding weaving machine. It will be understood that the drive of these cams, which are suitably offset angularly with respect to one another, on the common shaft, ensures control of the levers and the reciprocating vertical displacement of the heddle frames.
Experience has shown that, whenever the weaving machine stopped, either at the end of work or for the purpose of a momentary intervention on the machine or the cam mechanism, all the heddle frames had to be brought to the same height. To that end, the mechanisms are generally provided with a so-called "levelling" device which may take different forms, but of which the most current structure is that schematically shown in FIG. 1 of the drawings accompanying the present specification.
In this FIG. 1, reference 1 designates one of the rocking levers coupled to one of the heddle frames CL of the weaving machine, while reference 2 corresponds to the two rollers which are offset laterally with respect to each other to cooperate with the two tracks of a complementary cam 3, fitted on a drive shaft 4. The different rocking levers 1 of the mechanism are mounted idly on a common pin 5 oriented parallel to the shaft and it will be observed that each of the small-diameter ends 5a of this pin 5 is supported by an eccentric 6 of circular profile, housed in a cylindrical bore of a bearing 7 secured to the frame of the mechanism.
It will be readily appreciated that if, after the drive shaft 4 has stopped, the two eccentrics 6 are rotated in their bearings 7, the common pin 5 on which all the levers 1 pivot moves in the direction of the arrow appearing in FIG. 1. This recoil movement of the pin brings all the levers 1 in abutment against a fixed stop 8 of the frame 9 of the mechanism.
Consequently, all the rocking levers 1 are brought to the same angular orientation, whatever, at the moment of stop, the orientation of their complementary cam 3.
The present invention is based on the observation that the assembly of the ends 5a of the pin 5 inside the eccentrics 6 and the maintenance of the latter in the bearings 7 were detrimental to the rigidity of the point of fixation of the pin. During normal operation (weaving) of the mechanism, this pin is subjected to very high forces and to considerable vibratory effects. These forces and vibrations rapidly wear the pieces which support the pivot pin, generating the formation of rust in the bearings 7, as well as the appearance of a residual clearance detrimental to correct functioning of the mechanism assembly.
It is a principal object of the present invention to overcome this drawback.